1. Field of the Disclosure
The present disclosure relates to a scheme for transmitting a reference signal in a wireless communication system, and more particularly to a method and an apparatus for transmitting a reference signal in the light of an interference signal in a cellular communication system.
2. Description of the Related Art
In next generation wireless communication systems (for example, the Long Term Evolution-Advanced (LTE-A) system), cell coverage is relatively small when compared to conventional cellular environments. When various types of cells, such as conventional cells and femtocells operate in the same environment, non-uniform cell distribution occurs.
A User Equipment (UE) may receive not only a desired signal (also referred to as a “required signal”) from a serving cell, but also an undesired signal (also referred to as an “interference signal”) from another or “interfering” cell. In such an environment, inter-cell interference is the largest factor increasing packet error, thus reducing performance in the UE.
In an LTE wireless communication system, an evolved NodeB (eNB) transmit a reference signal, before transmitting data to the UE, such as a Channel State Information-Reference Signal (CSI-RS) in order to allow the UE to measure channel quality of the serving cell. Further, the eNB may use CSI-Interference Measurement (IM) to allow the UE to measure channel quality in consideration of channels of adjacent cells.
The UE uses the CSI-IM to determine a Channel Quality Indicator (CQI) and transmits feedback of the channel quality information to the eNB. The eNB transmits data to the UE based on the feedback. At this time, the eNB may also transmit a Cell-specific Reference Signal (CRS) on an Orthogonal Frequency Division Multiplex (OFDM) domain together with the data in order to allow the UE to estimate a channel (that is, the channel of a desired signal) required when the UE receives the data.
In order for the next generation UE (for example, the Long Term Evolution-Advanced (LTE-A) UE) to most efficiently remove an interference signal from the received signal to reduce a packet error of the desired signal, the UE needs the transmission scheme information of the interference signal as well as the channel information of the interference signal. While transmission scheme information of the interference signal may be estimated using the CSI-IM-, such estimation is limited because the CSI-IM reuses the CSI-RS resource pattern which is not suitable to estimate transmission schemes. A CSI-RS pattern is defined by location (or distribution) of resource element(s) used for transmitting the CSI reference signals.
Thus, in order to solve interference problems, there is a need for methods, apparatus, and systems for accurately transmission schemes of estimating interference signals received by the next generation UE.